The preparation of .alpha.-keto-carboxylic acids and their derivatives has been the subject of a large number of investigations. According to Rodd, The Chemistry of Carbon Compounds (1952 edition), Vol. 1, pages 227-229, the following methods of preparation are available:
gentle oxidation of .alpha.-hydroxyacids containing a secondary hydroxyl group, or by the enzymatic PA1 deamination of .alpha.-amino-acids; PA1 hydrolysis of an acyl cyanide; PA1 hydrolysis of .alpha.-oximino-esters; PA1 from glycidic acid esters on treatment with benzene saturated with boron trifluoride; PA1 from .alpha..beta.-dibromocarboxylic acids by forming a piperidine addition compound followed by hydrolysis; PA1 from .alpha.-keto-acetals by ultraviolet irradiation in the presence of N-bromosuccinimide; PA1 from .alpha.-bromomethylketones by boiling with selenium dioxide in absolute methanol or ethanol; PA1 from carboxylic acid esters by oxidation with selenium dioxide; PA1 permanganate oxidation of vinyl ketones; PA1 from carboxylic acid esters by condensation with oxalic ester followed by decarboxylation; PA1 from aldehydes via 5-alkylidene-2-thio-oxazolid-4-ones or by reaction with methyl methoxyacetate; PA1 hydrolysis of azlactones or acetamido-acrylic acids; hydrolysis of the reaction product of Grignard reagents on diethyl-oxamic ester; PA1 oxidation of .alpha.-hydroxyacid esters containing two .beta.-hydrogen atoms by N-bromosuccinimide in carbon tetrachloride to .beta.-bromo-.alpha.-keto-acid esters; and by the action of alkali on the dimethanesulphonates and ditoluene-p-sulphonates of .alpha.,.beta.-dihydroxycarboxylic acids.
In co-pending U.S. application, Ser. No. 353,473, entitled "PROCESS FOR PREPARING ALKYL .alpha.-KETO-CARBOXYLIC ACIDS FROM ALKYL HALIDES", filed Mar. 1, 1982, now abandoned, there is disclosed a method of preparing certain alkyl .alpha.-keto-carboxylic acids by reacting a primary alkyl halide in a liquid solvent medium with carbon monoxide in the presence of a metal carbonyl compound and an alkali metal inorganic base or an alkaline earth metal inorganic base. Further, in co-pending U.S. application, Ser. No. 405,817, entitled "PROCESS FOR PREPARING .beta.-SUBSTITUTED-.alpha.-KETO-CARBOXYLIC ACIDS", filed Aug. 6, 1982, there is disclosed the preparation of .beta.-substituted-.alpha.-keto-carboxylic acids by reacting a secondary alkyl halide in a liquid solvent medium with carbon monoxide in the presence of a metal carbonyl compound and an alkali metal inorganic base or an alkaline earth metal inorganic base. Still further, in co-pending U.S. application, Ser. No. 405,816, entitled "PREPARATION OF CYCLIC-KETO-ACIDS", filed Aug. 6, 1982, Pat. No. 4,473,706 there is disclosed a method of preparing certain cyclic-keto-acids by reacting a 1-bromoalkane in a liquid solvent medium with carbon monoxide in the presence of a metal carbonyl compound and an alkali metal inorganic base or an alkaline earth metal inorganic base. In co-pending U.S. application, Ser. No. 419,758, entitled "PREPARATION OF 6-CARBOXY-3,4-DIHYDRO-2H-PYRAN", filed on Sept. 20, 1982, abandoned, there is disclosed a process for preparing 6-carboxy-3,4-dihydro-2H-pyran by reacting a 1,4-dihalobutane in a liquid solvent medium with carbon monoxide in the presence of a metal carbonyl compound and an alkali metal inorganic base or an alkaline earth metal inorganic base. And, in co-pending U.S. application, Ser. No. 430,152, entitled "PREPARATION OF BIS-.alpha.-KETO-CARBOXYLIC ACIDS," filed Sept. 30, 1982, there is disclosed a process for preparing bis-.alpha.-keto acids by reacting a dihaloalkane in a liquid solvent medium with carbon monoxide at elevated temperature and pressure in the presence of a metal carbonyl compound and an alkali metal base or an alkaline earth metal base.